PROJECT SUMMARY This proposal is a first-in-human trial of a newly developed nanoparticle PET radiotracer that targets the natriuretic peptide receptor C (NPR-C), with the long-term potential to help to determine which asymptomatic patients with carotid artery stenosis might require surgery. Our research shows that NPR-C is differentially expressed in the deep intima of maximally diseased and vulnerable plaque segments and is expressed not only in vascular smooth muscle cells (VSMC) but also uniquely in the macrophages in this deep intimal region. Our findings show that the VSMC infiltrating into this deep carotid plaque intima and the macrophages developing there are pathologically unique, with differential expression of NPR-C relative to plaque severity. The objective of this proposal is to assess the performance of a newly developed PET radiotracer 64Cu-CANF- Comb 1) to reliably target NPR-C upregulated in atherosclerosis in humans in vivo and 2) to identify features of vulnerability in human carotid plaque. We will perform carotid PET-MR with 64Cu-CANF-Comb in both asymptomatic and symptomatic patients scheduled for carotid endarterectomy (CEA) surgery. We chose this patient population because CEA surgery will permit us to collect the plaque specimen after surgery to allow us to compare the PET imaging signal with tissue measurements of NPR-C expression and plaque morphology. To achieve this objective we will address the following Specific Aims: Aim 1. Demonstrate that 64Cu-CANF- Comb radiotracer can be used to target NPR-C upregulation in human atherosclerosis. After the PET- MR examination and the CEA surgery, we will collect each patient?s ex vivo CEA specimen. We will compare PET signal measurements in the diseased artery (plaque to be removed surgically) to NPR-C presence in the ex vivo specimen by IHC staining for NPR-C and RT-PCR. We will also perform IHC and RT-PCR of the distal (less diseased) CEA specimen as a control. We will colocalize for macrophages, VSMC and EC to determine NPR-C expression within cell populations. PET signal between the diseased and non-diseased contralateral artery and non-diseased portion of the ipsilateral artery will also be compared. Aim 2. Assess the utility of 64Cu-CANF-Comb to identify plaque with features of vulnerability. We will compare PET signal in the diseased artery to American Heart Association (AHA) classification for atherosclerosis vulnerability by grading of H&E stained ex vivo CEA specimens. PET signal will also be compared to the simultaneously acquired MR images for presence of atherosclerosis and MRI signal characteristics of fibrous cap, lipid pool and hemorrhage. We will also collect patient demographics, information regarding symptomatology, and risk factors. The results of this work will provide the necessary information on the potential of 64Cu-CANF-Comb to detect high-risk atherosclerotic plaque and, thus, will lay the foundation for larger studies to assess imaging findings in light of patient outcomes.